Slashdot videos: Now with more Slashdot!

View

Discuss

Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).

opticsorg writes "Infrared laser pulses could soon be used to determine whether someone is telling the truth or is under stress. In patent application WO 03/057003, US firm Defense Group describes a non-invasive polygraph machine that fires infrared pulses at the subject. The reflected and scattered pulses are gathered and analysed by a receiver. 'The receiver is connected to an information processing device capable of determining various physiological characteristics exhibited by the human subject,' say the authors." Whether "various physiological characteristics" are reliable signs of truth-telling is another issue, though.

Of, engaging in, or given to armed aggression: an invasive military force.

Marked by the tendency to spread, especially into healthy tissue: an invasive carcinoma.

Of or relating to a medical procedure in which a part of the body is entered, as by puncture or incision.

Tending to intrude or encroach, as upon privacy.

Polygraphs have consisted of blood-pressure monitors, pulse/respiration monitors/graphing, temperature, relative humidity/condensation on the epidermis, and as of late, retinal imaging. These are usually accomplised by a series of patches attached to the EXTERIOR of the patient's skin. No where, no how, is anything poked, prodded, or inserted.

If my invasive, you mean, less cumbersome, then sure, maybe. The patient would still have to breathe normally, and hold perfectly still (as to not alter the readings taken by the IR), which is really the only cumbersome thing about it.

the poly i was given (it was for a gov't security clearance, and part of a larger background investigation for that clearance) consisted of a pair of sensors on two of my fingers (IIRC, index and middle; detects sweating), a pair of cords across my chest and stomach (monitors breathing), and a blood pressure wrap reader on my upper arm (blood pressure (duh) and heart rate). and you get a nice leather reclining chair to sit in. no patches slapped to my skin anywhere.

And that is exactly the problem with the accuracy behind that test. It's all subjective...one tester sees something the other does not. Just because your heart rate goes up, doesn't mean you lied, etc... I still think it's a silly way to look for the truth.

No, it really couldn't be used on someone without their knowledge, as the target would have to remain seated, very very still, and have regular breathing. I think it'd be quite obvious what you, the patient, could do about it.

In all seriousness, many politicians are so used to lying that they'd probably be able to pass any lie detector test. If lying doesn't cause any stress, the lie detector can't detect it. But then, lie detection is a sham, anyway.

Sir Bedevere: There are ways of telling whether she is a witch.Peasant 1: Are there? Oh well, tell us!Sir Bedevere: Tell me. What do you do with witches?Peasant 1: Burn them!Sir Bedevere: And what do you burn, apart from witches?Peasant 1: More witches!Peasant 2: Wood!Sir Bedevere: Correct. Now, why do witches burn?Peasant 3:...because they're made of... wood?Sir Bedevere: Good. So how do you tell whether she is made of wood?Peasant 1: Build a bridge out of her!Sir Bedevere: But don't we also build bridges out of stone?Peasant 1: Oh yeah.Sir Bedevere: Now, does wood float in water?Peasant 1: No, no... Throw her into the pond!Sir Bedevere: No, no. What else floats in water?Peasant 1: Bread!Peasant 2: Apples!Peasant 3: Very small rocks!Peasant 2: Cherries! Great lumpy gravy!Peasant 3: Crutches!King Arthur: A Duck!Sir Bedevere: Exactly!

No. The problem is that the operator doesn't solely rely on what "shows up" on the machine. If they did, they could have a technician hook you up, turn the machine on, ask the questions and then submit the recorded info to an "expert" reader with just question numbers and time stamps. That won't work, however, because the reader won't be able to tell which questions you are supposed to be lying on and he won't be able to bluff you into revealing something. The machine is just a prop.

All "lie detector" tests are bogus because the results are always "subjective" to the machine's operator.

Not quite. Polygraphs can be valid under the right circumstances. They are reasonably accurate when used to ask questions about specific instances. Less so when they are used in hiring decision contexts. See this recent report from the National Academy of Science [nap.edu]. There are many effective countermeasures to "fool" a polygraph. I wouldn't want my future (guilt or innocence) to depend on one, but they are pretty good at recognizing when people have unusual reactions to stimuli. How they are interpreted (e.g., is that a 'lie' or just nervousness?) is another matter.

Anyone know when this concept was first used?

The use of the polygraph as lie detector was pioneered by psychologist Dr. William Moulton Marston. He may be more familiar to Slashdotters under his pseudonym Charles Moulton. That's the name he used when he created the comic book "Wonder Woman."

My brief look at the report you cite suggests that the researchers didn't do any experiments on their own but rather relied on a number of older experiments performed by a variety of organizations (correct me if I'm wrong).

Here's my first crack at how such an experiment should be handled:

Subjects should be representative of the population at large.

The questions should be chosen such that the truthful answer is "yes" about 1/2 the time across the subject population.

First, you are on the right track in pushing for a double-blind, methodologically sound study. However, the value of analyzing "a number of older experiments performed by a variety of organizations" should not be underestimated. In many ways a meta-analysis (evaluation of existing analyses) is actually more reliable than a single well designed study. No matter how well it is designed, any single study will have weaknesses -- they have a small number of subjects, the truths/lies are limited to

"In many ways a meta-analysis (evaluation of existing analyses) is actually more reliable than a single well designed study. No matter how well it is designed, any single study will have weaknesses -- they have a small number of subjects, the truths/lies are limited to a single domain, the time and location of the study has some unexpected influence on the results, etc."

Well that makes sense if each of the original studies is well designed, but if some of those studies are flawed then it's quite likely tha

the medical applications would be far more important and profitable then the "lie detecting" application. The fact that it wasn't a patent for a medical device suggests that it doesn't really measure anything meaningful.

Since there is no scientific standard for lie detectors (and the current ones are obviously a scam), you can use any kind of dubious technology you like. A medical device, however, has to demonstrate efficacy which is a much higher standard.

From a cog. neuro friend of mine, the argument is that when a person lies, there's a characteristic increase in bloodflow to a particular area of the brain. The IR system discussed in the story is used to measure this increase in bloodflow (which is the same thing that makes it useful in many other aspects of functional cognitive neuroscience; it's much cheaper than an fMRI). The real question here isn't really the machine or even the patent (God knows we get enough stupid patents around here). The real que

"The real question is whether or not this increase in bloodflow is 100% always indicative of lying and nothing BUT lying."

Well, unless one believes God is responsible the answer to that question is very likely to be no. What is the survival value of such a feature and how did it evolve?

I have to say I'm a bit sketical of the neural recognition argument as well. Exactly how close can two images be to be considered different by the brain? Obviously most visual information from a crime scene has nothing to d

I work with some of the authors you cited and I personally know most of the others. Near infrar-red spectroscopy and diffuse optical tomography are very good for measuring localized changes in blood oxygenation and volume (and, by inference, brain activation), but going from "you show activation in your right frontal cortex" to "you're lying" is a huge leap and way beyond the limi

So I knew this woman, a world class athlete, who also worked for the Department of Defense. For her Top Secret clearance she had to submit to a polygraph test every six months. On the day of one of her tests she arrived at the testing center having just worked out. Her pulse, respiration, and skin moisture were all a bit elevated, and the tester noted these abmornal readings to her. Now, one of her training techniques involved meditation, and she became adept at both mentally and physically relaxing in a very short amount of time. She went into her meditation routine and almost instantly her pulse and breathing rate dropped. The tester became angry with her, and told her to come back the next day. Now how hard can it be to learn to game the whole polygraph system?

Here's how a polygraph works. You measure certain things--not one thing, but many--and watch them over time. You look for deviations, not from some presupposed idea of "normal" but rather from the subject's baseline at that given instant.

Now, we're not talking about things like heart rate and respiration here, although those are observed. We're talking about things like galvanic skin response, which basically measures how sweaty you are at a very fine level of detail. These are not

Stop right there. You have just described the whole "science" of polography. The only reason it sticks around is there is enough money being pumped into it, that the purveyors of this snake oil can keep lots of people convinced that it works. The only thing it is useful for is convincing weak minded idiots that you actually have a way to see inside their heads, and get them to confess. Other than that, it is total bunk.

Sorry, bit of a typo there. Though I still stand by my assertion polygraph tests are junk science. If you haven't done so, I would recommend reading
The Lie Behind the Lie Detector [antipolygraph.org] (PDF), its a good read and very informative about polygraph tests and the like. Polygraphs are just the moden day version of a mystic. They don't do anything in and of themselves, they only convince people to confess, and are great for destroying someone's credibility because the media believes in them.

"Now, we're not talking about things like heart rate and respiration here, although those are observed. We're talking about things like galvanic skin response, which basically measures how sweaty you are at a very fine level of detail. These are not things you can change with rhythmic breathing or whatever. They are beyond your conscious and autonomic nervous systems and into the realm of physiological response."

How about you stop right there and go and read up a bit more. Galvanic skin responses can be

Great, another machine to do the impossible. I mean, really, how is this different than just looking someone in the eye when you ask them a question? Some people can lie convincingly and others can't. That's all there is to this system. Once you have a system, you CAN beat it, and some people do. Why don't we just accept that fact and get rid of polygraph machines? Either that, or have an experienced poker player read the results, as they have TONS of experience with poker-faces.

I can't not lie unconvincingly. I was arrested last year for being under the influence. I kept telling the guy that my heart rate was up cause I had walked about a half a mile, my mouth was dry because I had walked about half a mile, I was having "uncrontrollable muscle spasms" because I had walked a half a mile in shorts and a t-shirt in 40 to 50 degree F weather. I got very nervous after two more cop cars pulled up, one of them a drug specialist, which added to all the other symptoms. etc. etc. It all lea

is found in new techniques involving brain scans. A brain wave pattern called P300 ( "positive wave" 300 ms after onset ) has been discovered to be activated when a person looks at a familiar object ( the P300 hypothesis has gained very solid evidence since a few years ). So you can display some pictures to the accused person and embed in these actual crime scenes pictures, and then tell if the accusee is familiar with crime scene pictures ( like what the place looked like, weapons involved, etc. ). Of course, you have to display pictures that has not been released to the media and whatnot, but the uniqueness of the combinations needed to figure out that someone is involved in the crime is pretty high. Links here [nationalgeographic.com], here [sciscoop.com] and here [registerguard.com].

This polygraph stuff got to be thrown away at some point anyway, since it's based on reaction patterns that many people just don't have so its accuracy isn't high enough for the important task it has to do.

Well since you would have to be familiar to MANY ( think tens ) distinct pictures at the same time to get caught by P300 scanners, I guess this probability is pretty small, but there are chances it still might happen indeed so in essence, you are quite correct. Particularly in your conclusion, as you may expect I would by my sig;) In fact I wouldn't be surprised at all if such scanners were used as we're talking in Guantanamo. But not in Washington though... yet.

A brain wave pattern called P300 ( "positive wave" 300 ms after onset ) has been discovered to be activated when a person looks at a familiar object ( the P300 hypothesis has gained very solid evidence since a few years).

These are extremely controversial findings. I've had discussions with cognitive neuroscience researchers I work with and not one of them is totally convinced this is real yet.

I know they are, that's why I said it was an hypothesis. Having gained very solid evidence in the past years doesn't mean that a concept is beyond doubt, though it seems like new theories are always very controversial before they are widely accepted. Anyway, we'll see, and I'm sorry if my post left a "sure shot" kind of impression even if it seems to work according to what I know right now. Please link some pages about this controversy if you have some, I'd be pretty interested about that.

I just wonder if there is anyone out there who is combining the new insights we gain each week into the workings of th emind with the newest theories and practices of forensic investigation. Seems to me that we cannot rely on only one method. Although, ever more frequently, the police require less evidence to arrest, and judges/juries even less to convict. Oh well, I pity my great-grandchildren.